Assessment of genetic variability for grain micronutrient contents in sorghum [Sorghum bicolor (L.) Moench] for Biofortification

Abstract

Biofortification is a cost-effective and sustainable diet-based intervention to alleviate the foodrelated health problem of micronutrient malnourishment. Sorghum is a crop of sub-tropical and semi-arid regions of Africa and Asia where it is staple food for more than 500 million poor and most nutrition-insecure people. Breeding sorghum with more grain iron (Fe) and zinc (Zn), and regular consumption of such biofortified grains can improve the health status of predominantly sorghum eating populations. The availability of genetic variability for grain micronutrients is necessary for genetic manipulation. In order to assess the variability for grain micronutrients and identify suitable donors for breeding programme more than 400 sorghum genotypes comprising cultivars, hybrid parents, breeding lines and selected germplasm accessions were characterized for grain Fe and Zn. Good variation was observed for both micronutrients among the genotypes. The mean grain Fe ranged from 26.9 ppm (cultivars) to 37.6 ppm (exotic germplasm) while mean grain Zn ranged from 22.9 ppm (breeding lines) to 34.0 ppm (exotic germplasm). The exotic lines (n=39) comprising some accessions from sorghum mini-core collection showed a wide variation for grain Fe (25.7-62.2 ppm) while indigenous germplasm including landraces (n=260) had a wide range for Zn (9.4-43.7 ppm). A relatively narrow range was observed in cultivars (18.2-41.3 ppm Fe, 16.6-35.4 ppm Zn; n=61), parentals (18.0-38.5 ppm Fe, 18.0-37.5 ppm Zn; n=25) and breeding lines (19.1-40.0 ppm Fe, 15.4- 34.0 ppm Zn; n=25). The results indicate that suitable donors for Fe and Zn improvement can be identified from germplasm though it may be limited under improved agronomic backgrounds. The presence of good variability for grain micronutrients holds promise for recombination breeding to combine nutritional quality and high grain yield. The significant correlation (r=0.33-0.73) between Fe and Zn content indicates the possibility of simultaneous improvement. Based on the spectrum of variability identified an association mapping panel was constituted for GWAS for grain micronutrients.